(a) Technical Field
The present disclosure relates to a phase-change suspension fluid composition including polyethylene oxide particles and a method for manufacturing the same. More particularly, it relates to a phase-change suspension fluid composition prepared by dispersing polyethylene oxide particles into a solvent including water and one or more types of compounds selected from the group consisting of ethylene glycol and propylene glycol, and a method for manufacturing the same.
(b) Background Art
‘Phase-change fluids’ collectively refer to fluids of which mechanical and physical properties change by an external force applied, and are generally divided into shear thickening fluids (STF) and shear thinning fluids.
A shear thickening fluid (STF) is formed with concentrated suspension colloids in which unaggregated solid particles are dispersed into fluids, and viscosity is shown to distinctly increase when exceeding a critical shear rate [Xianzhou Zhang, Weihua Li, Gong, X. L., Smart Mater. Struct., Vol. 17, 015051 (2008)].
Under a high shear rate, viscosity of a shear thickening fluid (STF) increases, and the fluid becomes a solid-like suspension, and when shock stress is removed, the shear thickening fluid (STF) reversibly goes back to a liquid-like state quickly [Chang, L., Friedrich, K., Schlarb, A. K., Tanner, R., Ye, L., J Mater Sci, Vol. 46, 339-346 (2011)].
Meanwhile, a shear thinning fluid has a property that, in a normal flow, viscosity decreases as shear rate increases, and shear rate and viscosity are inversely proportional. In addition, a shear thinning fluid usually has a yield point, and such a material has no flowability under low shear stress, and has flowability (liquidity) only when a yield point is reached.
Particularly, a phase-change fluid is a fluid having a property that nanoparticles show a liquidification phenomenon under a high shear rate due to a sudden decrease of viscosity, and is generally present as being dispersed into a solvent such as ethylene glycol (EG), propylene glycol (PG), ethylene glycol (EG)/water or propylene glycol (PG)/water.
Nanoparticles have been a subject of much research due to a hydrocluster phenomenon between particles. However, a hydrocluster phenomenon between nanoparticles has a rather big difference compared to various theoretically proposed models depending on size of particles. Phase-change fluids show viscosity changes and yield stress behavior by an external force applied, and reaction is very fast and reversible with respect to the external force applied, and this is referred to as a ‘phase-change effect’. Such a phase-change fluid shows the behavior of a Bingham fluid having yield stress, and the yield stress may be obtained as the function of a shear rate.
These fluids may be used for a variable damping mechanism that is capable of controlling movement such as a brake, an engine mount, a damper and a bush, and power systems such as a brake and clutch, and are broadening their application to automotive and aviation industries, and robot industries as well.
As one example, an existing fluid-filled hydraulic bush is a component filling and sealing a fluid using cured rubber part, and may provide relatively more superior ride comfort caused by a spring-like property due to the combination of rubber elasticity and a fluid.
However, such a fluid-filled hydraulic bush has a limit, and this is due to the fact that all vehicle driving conditions having various changes may not be satisfied with just a constant amount of the fluid injected. In addition, fluids that have been used in the art are newtonian fluids showing a newtonian behavior having almost no viscosity changes by a frequency or a shear rate. Fluids absorb vibration when moving along a flow path, and such a fluid-filled hydraulic bush has a limit in that high speed operation stability and durability are inferior while having excellent ride comfort compared to general solid-type bushes.
Meanwhile, the Korean Patent Application Laid-Open Publication No. 10-2010-0125980 discloses a fluid-filled hydraulic bush capable of adjusting the amount of injected fluids. However, the constitution of the disclosed bush is not simple and, therefore, there is a limit in vehicle applications and a disadvantage in cost.
Generally, conventional hydraulic bushes have an excellent loss factor in a low frequency region compared to solid-type bushes, but may show an excessive increase in a dynamic spring constant due to a frequency increase, and in addition, when reviewing vehicle driving evaluation results, hydraulic bushes have a vibration isolation effect in a low frequency region compared to solid-type bushes, but may show an occurrence of excessive vertical vibration due to a frequency increase. Therefore, advantages of hydraulic bushes and advantages of solid-type bushes need to coexist.
Consequently, the needs for developing a fluid filled hydraulic bush and thereby developing an intelligent polymer-based dispersion fluid having advantages of a hydraulic bush in a low frequency region and advantages of a solid-type bush in a high frequency region, and capable of reversible phase changes by the vibration of vehicles have been raised.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.